feat: add verifier version to vsa

[mrjoelkamp]

summary

• creates a version fetcher interface
• adds verifier.version to VSA output
• adds version_test.go for version checker tests

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 4 lines in your changes missing coverage. Please review.

Project coverage is 70.75%. Comparing base (eda0b23) to head (7ff20a9).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
attestation/vsa.go	77.77%	1 Missing and 1 partial ⚠️
verify.go	81.81%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #201      +/-   ##
==========================================
+ Coverage   70.08%   70.75%   +0.66%     
==========================================
  Files          44       44              
  Lines        2577     2595      +18     
==========================================
+ Hits         1806     1836      +30     
+ Misses        474      457      -17     
- Partials      297      302       +5     

Flag	Coverage Δ
unittests	70.75% <85.71%> (+0.66%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jonnystoten]

LGTM